Close-up shots of Gary as a spider often show him surrounded by plants, even when long shots show him in an open space.
The plane that takes off is a completely different make than the one that crashes.
When Gary goes through the jungle with the girls, his shirt is ripped. When they arrive at the cabin, the shirt is not ripped.
At 9 minutes in the plane takes off as a twin engine Convair CV 240. In the air it is a four engine Douglas DC-4.
Close-ups of women screaming as their plane goes down are shot against a black screen, not an airplane interior.
A plane that size would have crashed into the Empire State Building before it could have gotten to the vantage point shown in the shot during the New York departure montage of stock footage.
From Los Angeles, the dancers stop in New York City on the way to Singapore.
In long shots near the end of the movie, Gary is not wearing his spider make-up.
Gary repeatedly refers to the gun as a revolver, even though it has no cylinder. Later, he loads a magazine into it, proving it is not a revolver.
One of the men takes the .45 AUTOMATIC PISTOL from one of the girls. He said something about having an unloaded REVOLVER. Also, with an automatic, you can't tell the magazine's empty.
When Mike Blackwood is talking about the plane crash on the phone, he smokes an unlit cigarette.
When they're chasing Spider Gary, one of the guys cycles the slide and it closes. He pulls the trigger and realizes it's empty. With that type of pistol, if the magazine's empty the slide stays open until the release lever is operated.